Shotgun theory.

Throw anything and everything at your players, cast as wide a net as possible by using a diverse cast of NPCs, and let them choose what they like and which NPCs they want to revisit.

>>46992124
I see.
But what if it's an important character I want to make a recurring one? Is there a way to make sure they're good enough for the players?

Semi-automatic theory.

Make a character and go balls to the walls with him, if the players don't click with him have him die off introduce a new guy. Rinse and repeat as needed.

Are there any more firearm theories?

>>46992065
If I need to come up with characters on the fly, I tend to essentially just sort of pull random adjectives, tropes, and ideas out of a hat and throw them onto blank slates with no rhyme or reason, and then try to justify these characters, flesh them out, give them a rounded personality, and make them believable.

For all the work I've put into pre-planned characters, a lot of the party's favorites have been just completely random hirelings thrown together on the spot who took on a life of their own.

>>46992065
Assholes. People in general will remember assholes and be more engaged with characters that they are in opposition to them. I never see my party as animated as when they're in a conversation with the dismissive head of the city guard or trying to get a deal out of that snooty merchant.

>>46993575
Bolt-action theory.

Create a character, note how your players respond to them, discard if needed, repeat.

>>46992124
This is my personaly favorite theory, I like to have a bit of a web where the NPCs can react and mention one another, but not directly interfere with eachother.

For Example:
>Slum Lord doesn't really like High-brow sneak, he cuts into profits, but he doesn't know where High-brow sneak resides.
>City Watch doesn't like Slum Lord's gang extorting and facilitating black markets, but have difficulty pulling his roots out of the slums.
>High-brow sneak is constantly trying to pull the wool over the eyes of the City Watch, he needs adventurers to distract and give false leads.

Eventually, if you manage to associate with one, you know of the others, and may not like them. Then again, you may appreciate another NPC and roll with his crew and philosophy.

This allows me to have a structured backstory for the area, and still improvise accordingly, without telling the PCs exactly what to do.

Unless they're really important and powerful characters, keep them simple.

I usually come up with a one sentence descriptor for the characters, then think of a secret or twist on that. For example in my Monsters and Other Childish Things game I have 'Bullied ulta-christian kid whose parents are getting divorced' then I added 'Has a terrifying monster that is making him more miserable and angry' for a secret.

They don't have to be as serious as that either, for example I have a 'meek arty kid' who is also really excitable and comes out of her shell when food is mentioned.

>>46992065
PCs enjoy NPCs who do things FOR them or TO them.

If your NPC is a total bro of a noble who heaps praise upon the party, invites them to fancy dinners, and gets them the kind of exclusive access they need to accomplish other stuff, the party will be absolutely in love with them and will completely put off killing that world-threatening lich of Noble Bro gets kidnapped one day.

On the other side of the spectrum, you can make a party love to HATE an NPC by having them harm the party. And not in the, "Oh, he attacks them," sense, or sends guards on them, or denies them access to some place, or speaks to another important NPC or group against the party. None of that shit, that's standard; the party thinks they're a dick but doesn't care. But how do you make this party move heaven and earth to want to murder this NPC? He steals some of their equipment in the night. Doesn't even have to be magic. He can steal ropes and wine skins and a +0 Slightly Dull Iron Longsword and the party will be F U R I O U S

>>46992456
No you can do want ever but if the players hate a key npcthey will have to deal of course there are those people love to hate